Saw blade for medical applications

ABSTRACT

The invention relates to a saw blade ( 1 ) for medical, in particular, surgical applications which comprises a recess ( 3 ) for mounting the saw blade inside a saw which exerts a saw movement, especially an oscillating saw movement, onto the saw blade ( 1 ). In order to improve the dynamic behavior of the saw blade ( 1 ), the invention provides that the flat area ( 6 ) of the saw blade ( 1 ) has a number of superficial impressions ( 5 ) of a defined contour.

[0001] The invention relates to a saw blade for medical, especially surgical applications, with a receiver for accommodating in a saw which applies a sawing motion, especially an oscillating sawing motion, to the saw blade.

[0002] Especially in the area of knee surgery is it necessary to cut the knee or knee sections and other tissue, such as cartilage or the like, for example when an artificial knee joint is implanted, by means of a saw. To do this, compressed air-driven or electrical saws (often made as battery-driven devices) are known which have a saw blade as is shown in FIG. 1.

[0003] The saw blade (1) is made as a thin sheet, therefore has a flat structure. On one end it has a sawtooth profile (2) which cuts the bone. The saw blade (1) is held in the saw by means of a receiver (3), for example with a multitooth profile. The saw applies a sawing motion to the saw blade. In this case the saw turns the saw blade around the axis of the receiver (3) back and forth by a small angle, causing the sawtooth profile (2) to move in an oscillating manner. In doing so the saw applies to the saw blade (1) such large angular movements on the receiver (3) that the lifting motion of the sawtooth profile (2) is only a few millimeters. The sawing frequency generally varies on the order of roughly 250 Hz.

[0004] Generic saw blades are known from U.S. Pat. No. 4,036,236 and EP 0 695 607 A1. In the saw blades described there it is provided that for purposes of stiffening or for purposes of reducing the weight of the saw blade there are ribs or grooves which run linearly from the receiver (3, see FIG. 1) as far as the sawtooth profile (2, see FIG. 1).

[0005] When bones are being cut, in the knee area what is important is making a cut as exact as possible. The required precision varies less than a millimeter. Known saw blades engender problems in this respect:

[0006] The saw blade during sawing must oscillate with such a high frequency that the dynamic forces cause vibration of the saw blade in the direction of the normal to the flat area of the saw blade. In the resonant area the vibration amplitude can become so large that in spite of the use of templates which exactly guide the saw the required sawing precision cannot be maintained. The cut becomes inexact; this entails the corresponding consequences in surgery.

[0007] Another disadvantage is caused by the fact that the saw being used is exposed to high dynamic stress so that especially its bearings are subject to high loads. In the saws which are conventionally in use it is therefore necessary relatively often to replace their bearings so that sufficient accuracy can be achieved at all.

[0008] Reducing the thickness of the saw blade does not yield any major benefit. Then the dynamic effect as a result of the reduced mass of the saw blade is less, but deflection of the blade is increased when working forces are applied.

[0009] Therefore the object of the invention is to further develop a saw blade of the generic type such that it has much improved dynamic behavior and nevertheless has high static stiffness. Thus it should become possible to make precise cuts through bones. Furthermore the durability of the saw will be improved, especially with respect to its bearings.

[0010] Achieving this object by the invention is characterized in that the flat area of the saw blade has a number of surface impressions of defined contour which are aligned in an oriented arrangement to one another and along a straight line, the line being aligned at an angle to the lengthwise axis of the saw blade.

[0011] The impressions in the surface of the saw blade influence the ability of the blade to transport or relay vibrations. That is, with the impressions it is possible to influence the dynamic behavior of the saw blade. In this way the vibration behavior of the saw blade can be greatly reduced in operation; the precision of the cut is increased accordingly.

[0012] Preferably the surface impressions are located on both sides of the flat area of the saw blade; specifically they can be located opposite one another on the two sides of the flat area.

[0013] Influencing the dynamic behavior is especially benefited by the impressions since the surface impressions are aligned in an oriented arrangement to one another and along a straight line. The line is aligned at an angle to the lengthwise axis of the saw blade.

[0014] The angle is preferably between 15° and 45°, especially between 25° and 35°.

[0015] For the contour of the surface impressions there can be different geometries. First of all, rectangles are possible, preferably the length of the rectangle being at least 1.5 times, especially at least twice, the width of the rectangle.

[0016] Alternatively surface impression in the form of squares, triangles, circles or polygons are possible. Here the side lengths or diameters of the surface impressions are advantageously between 1.5 mm and 30 mm, preferably between 2 mm and 10 mm.

[0017] Furthermore, dynamic properties are especially improved when the surface impressions are located at equidistant intervals to one another. The distance between two surface impressions can be between 0.5 mm and 10 mm, especially between 1 mm and 5 mm.

[0018] The depth of the surface impressions runs preferably to values between 0.05 mm to 0.5 mm, preferably 0.1 mm and 0.2 mm.

[0019] The saw blade according to the development consists of high-strength steel, high-alloy chromium steel being intended. The tensile strength of the steel should be at least 1200 N/mm², the surface hardness of the saw blade at least 60 HRC (HRC is the Rockwell hardness).

[0020] The embodiment of the saw blade as claimed in the invention leads to the vibrations being reliably damped at the start of the building-up process. Thus over the entire frequency range with which the saw blade is excited during the sawing process the blade does not tend to vibration perpendicular to the blade surface. The cutting precision is thus significantly increased.

[0021] Embodiments of the invention are shown in the drawings.

[0022]FIG. 1 schematically shows an overhead view of the saw blade according to the prior art.

[0023]FIG. 2 shows a view of the saw blade corresponding to FIG. 1 according to a first version of the invention.

[0024]FIG. 3 shows section A-B as shown in FIG. 2.

[0025]FIG. 4 shows an alternative execution of the approach shown in FIG. 2.

[0026]FIG. 5 shows a saw blade with another horizontal projection.

[0027]FIG. 6 finally shows another saw blade for a sabre saw.

[0028] The saw blade shown in FIG. 2 in an overhead view consists of a flat base body of high-alloy chromium steel. The saw blade 1 has a lengthwise axis 4. On one end the saw blade 1 is provided with a sawtooth profile 2 which is made for example with a laser cutting process. On the other end a receiver 3 is machined which is made here as a multitooth profile which interacts with the corresponding counterpiece of the saw which is not shown.

[0029] The saw turns the saw blade 1 in operation around the center point of the receiver 3 in the plane of the flat area, by which the sawtooth profile 2 is moved back and forth and thus can cut through bone and other tissue.

[0030] To improve the dynamic behavior, the surface of the saw blade is provided with a host of surface impressions 5. In the embodiment shown in FIG. 2 the impressions 5 are made in the form of small rectangles.

[0031] As can be recognized, the individual rectangles thus have an alignment oriented to one another. They are positioned at short distances behind one another along a line 7 which is shown as a broken line in FIG. 2. The line 7 in turn is located at an angle α to the lengthwise axis 4. The angle α is preferably 30° here.

[0032] As already mentioned, the added elements 5 are impressions on the surface of the saw blade 1. This is apparent from FIG. 3. There the section A-B as shown in FIG. 2 is shown. With an embossing tool which is not shown the impressions 5 have been embossed on either side of the flat areas 6, the respective impressions 5 lying opposite one another on both sides of the saw blade 1. This results in that between the impressions 5 a compacted or compressed material area 8 forms which as a result of material compression has the property of deflecting vibration-induced excitations. The special arrangement of the impressions 5 along the angularly aligned line 7 (see FIG. 2) causes deflection of the vibration excitation “out of the saw blade”, for which reasons the dynamic behavior of the saw blade 1 is significantly improved.

[0033] The impressions 5 can also be made in an alternate form.

[0034] Instead of the rectangular cross sectional shape in FIG. 3 there can also be trough-shaped or similar impressions which enable a continuous material transition from the flat area 6 into the impression area. In this case the impressions 5 can be produced using a crowned embossing die.

[0035]FIG. 4 shows one version of the embodiment as shown in FIG. 2. Here the impressions 5 are made in the form of circles. The circles are again aligned along a straight line which is aligned by the angle α to the axis 4.

[0036] It is shown in FIG. 5 that the concept of the invention can be applied to other basic contours of the saw blade 1. Here the saw blade 1 is made in the manner of a hammerhead in the area of the sawtooth profile 2.

[0037] The concept of the invention can furthermore be applied to other types of medical saws as follows from FIG. 6. A saw blade 1 is shown there which is used in a saber saw. The surface impressions 5 are also aligned in an oriented manner, so that the vibrations which build up are deflected out of the saw blade 1. Here the dynamic behavior of the saw blade 1 in operation is also greatly improved.

[0038] The surface impressions 5 can be efficiently made by an embossing process. The saw blade 1 can thus be economically produced. 

1. Saw blade (1) for medical, especially surgical applications, with a receiver (3) for accommodating in a saw which applies a sawing motion, especially an oscillating sawing motion, to the saw blade (1), characterized in that the flat area (6) of the saw blade (1) has a number of surface impressions (5) of defined contour which are aligned in an oriented arrangement to one another and along a straight line, the line being aligned at an angle (α) to the lengthwise axis (4) of the saw blade (1).
 2. Saw blade as claimed in claim 1, wherein there are surface impressions (5) on both sides of the flat area (6) of the saw blade (1).
 3. Saw blade as claimed in claim 1 or 2, wherein the surface impressions (5) are each located opposite one another on both sides of the flat area (6) of the saw blade (1).
 4. Saw blade as claimed in one of claims 1 to 3, wherein the angle (a) is between 15° and 45°, preferably between 25° and 35°.
 5. Saw blade as claimed in one of claims 1 to 4, wherein the surface impressions (5) have the outline of rectangles.
 6. Saw blade as claimed in claim 5, wherein the length of the rectangle is at least 1.5 times, preferably at least twice the width of the rectangle.
 7. Saw blade as claimed in one of claims 1 to 4, wherein the surface impressions (5) have the outline of squares.
 8. Saw blade as claimed in one of claims 1 to 4, wherein the surface impressions (5) have the outline of triangles.
 9. Saw blade as claimed in one of claims 1 to 4, wherein the surface impressions (5) have the outline of circles.
 10. Saw blade as claimed in one of claims 1 to 4, wherein the surface impressions (5) have the outline of polygons.
 11. Saw blade as claimed in one of claims 5 to 10, wherein the side lengths or diameters of the surface impressions (5) are between 1.5 mm and 30 mm, preferably between 2 mm and 10 mm.
 12. Saw blade as claimed in one of claims 1 to 11, wherein the surface impressions (5) are located at equidistant intervals to one another.
 13. Saw blade as claimed in one of claims 1 to 12, wherein the distance between two surface impressions (5) is between 0.5 mm and 10 mm, especially between 1 mm and 5 mm.
 14. Saw blade as claimed in one of claims 1 to 13, wherein the depth of the surface impressions (5) is preferably between 0.05 mm to 0.5 mm, preferably 0.1 mm and 0.2 mm.
 15. Saw blade as claimed in one of claims 1 to 14, wherein the saw blade consists of high strength steel.
 16. Saw blade as claimed in claim 15, wherein the steel is a high-alloy chromium steel.
 17. Saw blade as claimed in claim 15 or 16, wherein the tensile strength of the steel is at least 1200 N/mm².
 18. Saw blade as claimed in one of claims 1 to 17, wherein the surface hardness of the saw blade is at least 60 HRC. 